The present invention relates to maintaining and retrieving information in conjunction with the operation and maintenance of an operating plant. In particular it relates to a computerized system for maintaining the records and knowledge for overseeing plant operation and maintenance.
All operating plants must provide for appropriate maintenance of components. Particularly in those situations where the plant either can not be shut down or it is not desirable for economic or other reasons to shut it down, provision must be made for safely isolating and taking out of service components that must either be serviced or replaced. Generally speaking, this is particularly true of power generating plants, chemical and pharmaceutical plants, refineries, and the like.
The invention can best be described and understood in conjunction with the operation and maintenance of an atomic energy (nuclear) power plant. While the present invention was made to oversee the operation and maintenance of one such plant, and will be described with reference thereto, it should be understood that it is adaptable and applicable to use with various other operating plants.
In the maintenance of any operating plant it is necessary to consider safety regulations, both governmental and in house, environmental regulations and concerns, appropriate scheduling, logistics, and so forth. These considerations are particularly critical in the operation of an atomic energy power plant.
Prior to the present invention, several separate computerized databases were created and accessed by appropriate plant managers, and hard copy records and work sheets were used for manual data entry and control. For the nuclear plant under discussion, there was a Power Plant Maintenance Information System referred to hereinafter by the acronym "PPMIS"; the Nuclear Plant Master Equipment List referred to hereinafter by the acronym "NPMEL"; and the Project Resource Evaluation and Management Information System referred to hereinafter by the acronym "PREMIS". Also in use was a computer database containing "Tag-Out" information.
"Tag-Out" refers to the practice of attaching warning tags (e.g., stop work tags) to components to caution workers that the setting or operation of that component should not be altered without getting prior approval that it is safe to alter the operative condition. When a component is to be serviced it must be isolated from the system in which it is used. Valves may have to be opened or closed, switches may have to be secured in a particular condition, and all of these operations usually have to be performed in a prescribed sequence. The components that must be secured in a particular mode to isolate a selected component are said to establish the boundary for isolation, and this group of boundary components are referred to as a "Tag-Out".
To add or remove a "Tag-Out", the components that form the boundary for isolation have to be identified from process drawings (e.g., electrical and mechanical schematics). The position in which components in the isolation boundary must be placed is identified. The sequence for placing components in the proper position for the isolation is determined. The planned Tag-Out must be cross checked with other work to determine if there are conflicts (e.g., the same valve must be open for one Tag-Out and closed for another Tag-Out). The proposed Tag-Out is considered relative to operational procedures and relative to possible technical specification limitations. Finally, the Tag-Out is verified for implementation.
The majority of the tasks are performed by people using knowledge, experience and plant documents (drawings, procedures and references such as the technical specifications). Because of the human element and the tremendous amount of information that is combined from multiple sources, errors are made quite often. Moreover, the process is labor intensive and time consuming. All mistakes in the process result in considerable rework. Also, errors can lead to injury or death to personnel, damage to plant equipment, loss in plant reliability, and so forth.
Generally, maintenance is planned by: a) identifying from drawings equipment that must be placed in a particular state (for example, "closed" for a valve or "open" for an electrical breaker) to isolate another component for maintenance; b) determining the impact upon the system or plant from written procedures when available or, more frequently, from understanding of component operation; and c) determining by logical thought the sequence of safely placing the boundary components in the isolation states.
Notwithstanding the existence of the databases mentioned above, heretofore the procedure involved first identifying all of the components that are needed to completely isolate the component that is to be serviced. This was accomplished by visual examination of drawings and looking for components (e.g., valves and breakers) that may be isolated. Multiple sets of drawings had to be examined such as flow diagrams, piping and instrumentation diagrams, electric system schematic diagrams, and electric wiring diagrams. Having located the various components to provide the isolation boundary, it was necessary to determine through logical thought processes the position or state that each of the selected components had to assume. Next, it was necessary to determine logically if such positions or states would conflict with the positions or states that would be required for safe maintenance, safe operation or to satisfy regulatory requirements.